/*
 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */ 


import java.io.*;
import java.security.*;
import java.security.spec.*;

class VerSig {

    public static void main(String[] args) {

        /* Verify a DSA signature */

        if (args.length != 3) {
            System.out.println("Usage: VerSig publickeyfile signaturefile datafile");
            }
        else try{

            /* import encoded public key */

            FileInputStream keyfis = new FileInputStream(args[0]);
            byte[] encKey = new byte[keyfis.available()];  
            keyfis.read(encKey);

            keyfis.close();

            X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(encKey);

            KeyFactory keyFactory = KeyFactory.getInstance("DSA", "SUN");
            PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);

            /* input the signature bytes */
            FileInputStream sigfis = new FileInputStream(args[1]);
            byte[] sigToVerify = new byte[sigfis.available()]; 
            sigfis.read(sigToVerify );

            sigfis.close();

            /* create a Signature object and initialize it with the public key */
            Signature sig = Signature.getInstance("SHA1withDSA", "SUN");
            sig.initVerify(pubKey);

            /* Update and verify the data */

            FileInputStream datafis = new FileInputStream(args[2]);
            BufferedInputStream bufin = new BufferedInputStream(datafis);

            byte[] buffer = new byte[1024];
            int len;
            while (bufin.available() != 0) {
                len = bufin.read(buffer);
                sig.update(buffer, 0, len);
                };

            bufin.close();


            boolean verifies = sig.verify(sigToVerify);

            System.out.println("signature verifies: " + verifies);


        } catch (Exception e) {
            System.err.println("Caught exception " + e.toString());
};

    }

}